Dental handpiece with improved grease retention

ABSTRACT

A dental handpiece has a rotor assembly ( 10 ) with a rotor ( 15   a ) and two ball bearing assemblies ( 13, 14 ) supporting a rotor ( 15   a ). At least one of the ball bearing assemblies ( 13, 14 ) has a ball ( 20 ) and a retainer ( 21 ). The retainer ( 21 ) has at least one grease retaining groove ( 30, 50 ) or void ( 51 ) therein.

RELATED APPLICATIONS

This application is a Continuation In Part of U.S. patent applicationSer. No. 11/151,933 filed Jun. 13, 2005, which is a Continuationapplication of U.S. patent application Ser. No. 10/371,033 (CaseMID-30D) filed Feb. 20, 2003, which claims the benefit from ProvisionalApplication No. 60/359,962 filed Feb. 27, 2002.

TECHNICAL FIELD

The present invention is directed toward dental handpieces of the typeemploying greased bearings. More particularly, the invention is directedtoward a dental handpiece having improved grease retention even withrepeated exposure to conventional sterilization practices. The handpiecehas at least one bearing retainer with a unique geometry of greaseretention grooves.

BACKGROUND OF THE INVENTION

Dental handpieces of many types, including the air-driven type are knownto have an outer housing which often includes a neck portion. Within thechamber of the housing is a rotor adapted to be driven by air suppliedthrough the handle and neck. The housing often includes upper and loweropenings that are axially aligned with a rotor being supported forrotation by upper and lower bearing assemblies. The rotor often includesa bur tube that extends substantially between the openings and has acentral bore axially aligned with those openings. The lower end of thebore conventionally receives a gripping chuck that is often fixed to thebur tube. Such a dental handpiece is disclosed for example, in U.S. Pat.No. 4,089,115 which is hereby incorporated by reference for suchdisclosure.

The bearing assemblies often include a plurality of balls held within aretainer. Foe example, U.S. Pat. No. 3,994,544 discloses such a ball andretainer bearing assembly, and is hereby incorporated by reference forsuch disclosure. It was a stated object of the invention of that patentto provide for a bearing for a high-speed turbine, such as may be usedin a dental handpiece, and wherein the balls and retainer assembly weregreased. Greasing of the bearing assemblies has proven to be a usefuland desirable method of reducing friction between the balls and theirsupporting structure, leading to reduced wear, noise, heat build-upduring use and overall improved operability of the handpieces. However,dental handpieces are unique in their use of greased bearings because oftheir intended use. More particularly, dental handpieces are often runat high speeds of up to 450,000 rpm or greater. Further, after each use,the handpiece must be carefully sterilized before it is used withanother patient. Sterilization processes often include the use of hightemperature, humidity and pressure. Such processes rapidly degrade thegrease packing associated with the handpiece bearings. The grease mustoften be repacked repaired or otherwise compensated for, which is a timeconsuming and often difficult job.

A need exists therefore for a grease packed dental handpiece withimproved grease retention characteristics. The handpiece should beimproved with respect to the length of time and number of sterilizationand use procedures that it can be subjected to before for example,repacking is necessary. The dental professional and the patient wouldboth benefit from such a handpiece in the form of improved productquality, improved dental procedure efficiency and overall reduced dentalprocedure costs.

SUMMARY OF THE INVENTION

It is therefore, an object of the invention to provide a dentalhandpiece.

It is another object of the invention to provide an improvedgrease-packed dental handpiece.

It is another object of the invention to provide a dental handpieceimproved with respect to its grease retention characteristics.

These and other objects of the invention that will become apparent fromthe following discussion, are accomplished by the invention ashereinafter described and claimed.

These and other objects of the invention, which will become apparentfrom the present disclosure, are carried out by the invention ashereinafter described.

In general, a dental handpiece of the type having a rotary membersupported by at least one bearing assembly, wherein said at least onebearing assembly has an annular retainer and a plurality of balls atleast partially supported by said annular retainer, the improvementcomprising a grease retention groove in a surface of said annularretainer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of the rotor assembly 10, having aretainer element according to the present invention.

FIG. 2 is a perspective view of a retainer element according to thepresent invention.

FIG. 3 is a perspective view of an alternative embodiment of a retainerelement according to the present invention.

FIG. 4 is a perspective view of an alternative embodiment of a retainerelement according to the present invention.

FIG. 5 is a perspective view of an alternative embodiment of a retainerelement according to the present invention.

PREFERRED EMBODIMENTS FOR CARRYING OUT THE INVENTION

The present invention has application to any dental handpiece where itis advantageous to provide for improved grease retention properties.Such properties are especially advantageous in dental handpieces thatare subjected to repeated use and sterilization under harsh conditionsof high heat and moisture. The present invention may therefore, findapplication in any handpiece driven by electric motor, pressurized airor the like.

The handpiece selected for illustration is an air-driven rotor assembly10 having a pair of ball bearing assemblies 13 and 14 supporting rotor15 a for rotation, and including a conventional chuck 15. The rotorincludes any conventional driving means such as for example, anair-turbine 16 for rotatably driving rotor 15 a. The turbine depicted inFIG. 1 is a radial-flow turbine that is driven by air, but of course,can be of any conventional design.

Bearing assemblies 13 and 14 are each provided with a plurality of balls20 supported by annular retainers 21 and 22. The invention will beexemplified with reference to bearing retainer 21, it being understoodthat at least one and preferably both retainers 21 and 22 have thestructure according to the present invention.

Dental handpiece rotor assembly 10 is of the type wherein grease (notshown) is packed into the head, such that the balls are physicallycoated or contacted by the grease during use. As turbine 16 causes rotor15 a to rotate, rotor 15 a is supported by bearing assemblies 13 and 14.Hence, balls 20 support rotation of rotor 15 a. In other words, rotor 15a is journaled within bearing assemblies 13 and 14. As is conventional,balls 20 are rollingly supported by retainer 21 within ball apertures 23which prevents adjacent balls 20 from touching each other. The presenceof grease helps to reduce the friction encountered between thecontacting parts. According to the present invention, retainer 21 hasstructure to facilitate the physical retention of grease in proximity tosuch contacting parts, assuring its continued, affective presence evenafter repeated use and sterilizations, at least compared to conventionalhandpieces. By “at least partially supported” as used herein withrespect to the balls 20 and the retainer 21 it is meant that the ballapertures 23 prevent adjacent balls 20 from physically contacting ortouching each other.

In order to facilitate such grease retention, retainer 21 is providedwith at least one groove 30 in a surface thereof. By “surface” it ismeant some external surface. For example, retainer 21 shown in FIG. 2has an inner surface 31, and outer surface 32, ball retention aperturesurfaces 33, upper surfaces 34 and lower surfaces 35. Further, retainer21 shown in FIG. 2 has an inner annular groove 30 a disposed on innersurface 31, a first outer annular groove 30 b disposed upon outersurface 32, and a second outer annular groove 30 c also disposed uponouter surface 32.

In the embodiment of the invention depicted in FIG. 2, first outerannular groove 30 b and second outer annular groove 30 c are spacedapart such that ball apertures 23 are positioned therebetween. Further,there is preferably an overlapping or cut-away portion of each groove 30and a portion of each ball aperture 23, such as at overlapping portion40. Overlapping portion 40 allows for ingress of grease held within agroove 30 into ball aperture 23 to thereby lubricate a ball 20 heldtherein.

It will be appreciated that any number, size, depth, location or shapeof groove 30 is within the scope of the invention. Further, as will bemore fully explored below, the invention can be carried out with otherthan a groove, such as with a hole, aperture, depression, detent,dimple, cut, void, slice or the like, and need not be annular or evenregularly spaced.

For example, FIG. 3 illustrates an embodiment of the present inventionhaving first and second outer annular grooves 30 b and 30 c, but noinner groove.

FIG. 4 illustrates an embodiment of the invention wherein a plurality ofstraight grooves 50 extending between upper and lower surfaces 34 and35. In this illustration, straight grooves 50 are regularly spacedbetween each ball aperture 23, but need not be so. Further, grooves 50need not be straight but may be any shape or configuration.

FIG. 5 illustrates a retainer 21 having an inner annular groove 30 a,and also having a plurality of grease retaining dimples or voids 51, inthis case, positioned within ball aperture surfaces 33. It will beappreciated that voids 51 can be positioned upon any external surface ofretainer 21 and still be within the scope of the invention, and that anynumber of such voids 51 may be employed.

The size, shape, depth, spacing and location of all grooves 30, 50 orvoids 51 may be varied and all fall within the scope of the invention.Each such aspect will be varied based upon the optimal end useconditions of the device with which the given retainer 21 is employed.

It has been found that the presence of grooves 30, 50 or voids such asvoids 51, improve the useful life of a grease packed handpiece withwhich they are employed. It is believed that the grooves 30, 50 or voids51 provide a place for excess amounts of greased to congregate orcollect, beyond the amount of grease otherwise capable of beingpositioned proximate to the respective components. This improvedcollection helps to ensure a supply of grease beyond that ofconventional dental handpieces. A handpiece according to the presentinvention thus has a longer life of use and sterilization, as comparedto an otherwise similar handpiece without the inventive structure. Thisserves to improve the overall bearing life and hence the overall life ofthe handpiece, as well as ensuring that noise and friction reduction aremaintained for longer periods of time than is otherwise possible.

It should be apparent therefore, that the present invention provides anadvantage and an improvement over known dental handpieces. While in theforegoing, embodiments of the invention have been disclosed inconsiderable detail for purposes of illustration, it will be understoodby those skilled in the art that many of these details may be variedwithout departing from the spirit and scope of the invention.

1. A dental handpiece of the type having a rotary member supported by atleast one bearing assembly, wherein said at least one bearing assemblyhas an annular retainer and a plurality of balls at least partiallysupported by said annular retainer, the improvement comprising a greaseretention groove in a surface of said annular retainer.